Yes, though, by doing so, you can't use the automatic integration via the "Dial page or SMS service" option as a trigger action in Orion; you'll need to configure your trigger actions as 'execute an external program'.

Then, on whatever system you install PageGate, you'll need to share the GetAscii polling directory to make it available to the Orion server. Then, in Orion, your "execute an external program" trigger action would need to be formatted like this: